1. Field of the Invention
The present invention relates to a micro-accelerometer for sensing and measuring accelerations or the other forces.
2. Description of the Related Art
Micro-accelerometers are utilized in the fields of various engineering applications such as the automotive industry, navigation systems, military industry, robot systems, electronic appliances and toys, due to their small size, low price, and high performance.
Micro-accelerometers typically include a sensor for sensing a proof mass and movements thereof. Micro-accelerometers can be classified as an electric capacity sensing type, a piezoresistance sensing type, a piezoelectricity sensing type and an optical sensing type according to the constructions and sensing methods thereof.
The electric capacity sensing type micro-accelerometers have an advantage in that they require less power and space and have a high sensitivity. However, they also have a disadvantage in that they are affected by electromagnetic interference and parasitic electromagnetic forces. Representative examples of such micro-accelerometers are described in U.S. Pat. Nos. 6,705,166, 6,311,556 and 6,305,714.
The piezoresistance sensing type micro-accelerometers have an advantage in that the production thereof is simple and that they have a compact readout circuit. However, they also have a disadvantage in that they have an inferior sensitivity and are affected by the ambient temperature. Representative examples of such micro-accelerometers are described in U.S. Pat. Nos. 6,683,558, 5,539,236 and 5,425,841.
The piezoelectricity sensing type micro-accelerometers have an advantage in that the production thereof is simple and that they have a simple readout circuit. However, they also have a disadvantage in that they suffer from the leakage of electronic charge and are affected by the ambient temperature. Representative examples of such micro-accelerometers are described in U.S. Pat. Nos. 6,655,211, 6,038,924 and 5,869,762.
Finally, the optical sensing type micro-accelerometers have a high sensitivity and their operation is effectively performed. However, they have a disadvantage in that their prices are very high. Representative examples of such micro-accelerometers are described in U.S. Pat. Nos. 6,628,400, 6,581,465 and 6,473,187.